Flow bodies as parts of a vehicle or of another apparatus subjected to a surrounding flow are often required to show aerodynamic characteristics that result in a substantially fully attached flow in a variety of flow conditions. For example, commercial aircraft are designed for wide flow velocity and altitude ranges. In boundary conditions, such as during high lift flight, it is possible to use active flow control systems for preventing flow separation from an aircraft wing or other surfaces. In comparison to conventional surfaces active flow control can lead to an increased lift by eliminating separations, while holding the angle of attack constant, or by delaying the stall of a particular surface to higher degrees of flow incidence, consequently increasing the lift as well. This is expedient and advantageous especially for wings of an aircraft, vertical or horizontal tail planes or other control surfaces attached to a part of an aircraft.
It is known to employ fluidic actuators for influencing the flow along a flow surface of a flow body. These fluidic actuators maybe realized in such a way that they provide a pulsed ejection from opening in the flow surfaces. This ejection is able to delay separations to higher flow incident angles by introducing vortical structures, which convect downstream of the flow element thus energizing the otherwise separated flow area. By optimizing the pulsation frequency and the momentum injection through the openings according to the local flow phenomena a highly efficient active flow control system can be created. Usually, these fluidic actuators utilize valves or other active flow influencing means for the provision of the pulsed flow.
The leading edge separation of flow during high aerodynamic loads associated with large flow incidence angles is usually suppressed by mechanical devices such as slats and Krueger flaps. These usually comprise a distinct technical complexity, movable mechanical components and therefore produce high manufacturing and maintenance costs. Conventional leading edge high lift devices make use of several aerodynamic effects, which increase the incident range for which the flow can be kept attached to the surface of the trailing element. The most important effect thereof is the reduction of the low pressure suction peak of the following element, thus decreasing the destabilizing pressure rise on this element. To a certain extent also passive vortex generators are capable of keeping the flow attached to high flow incident angles. This is done by the creation of stream-wise vortex lines, which introduce energy into the boundary layer. However, usually those passive devices are not able to achieve the same gains, created by mechanic leading edge high lift devices and also produce parasitic drag in flight states where they are not necessary. Furthermore, in some regions, e.g. outboard areas of aircraft wings or other flow surfaces, these conventional methods may not be used, primarily through the lack of necessary installation space. Therefore, flow separation is usually the limiting factor for the design of those regions. Consequently a push of those natural boundaries would be beneficial for the overall efficiency of e.g. an aircraft.